Online Evaluation  
Following common practice [1]}, [2]}, [3]}, [4]}, we also submit an ensemble of four “AoANet w/ Dynamic Prophet Attention” models to online MSCOCO evaluation serverhttps://competitions.codalab.org/competitions/3221#results.
For the leaderboard, CIDEr-c40, specially designed for image captioning, is the default ranking metric, which is more convincing than CIDEr-c5, as shown in [5]} that CIDEr achieves higher correlation with human judgment when more reference sentences are given.
The results of our approach and the top-performing published works on the leaderboard are reported on Table REF .
As we can see, we outperform all the works in terms of CIDEr-c40 and rank the 1st.
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